1. Field of the Invention
The present invention relates to a communication control apparatus, a portable communication apparatus and a communication control method, all for performing communications via a communication satellite and a ground radio base station, and more particularly to a fitted-on type miniature communication control system such as, a wrist watch type system.
2. Description of the Related Art
Mobile radiotelephone systems like an automobile telephone and a cellular telephone are nowadays utilized widely. In recent years, new mobile radiotelephone systems such as a PHS (Personal Handy-phone System) in Japan and a GSM (Global System for Mobile Communication) in Europe have been developed. Now the miniaturization of the mobile radiotelephone systems and an improvement in their performances are being carried out in accordance with the digitization of communication/call data. As a result, a small-sized communication terminal having a high performance can be used for sending and receiving data to and from a facsimile and a personal computer.
A system utilizing a communication satellite (geostationary satellite), which moves in a stationary orbit, is mainly used as a satellite communication system. In a satellite communication system utilizing a geostationary satellite, a communication terminal requires a large-sized parabola antenna. A worldwide mobile communication system employing, in place of a geostationary satellite, a plurality of non-geostationary satellites which move in orbits lower in height than the orbit of the geostationary satellite, is being planned now. Among others, considerations and experiments have already been initiated for plans such as the xe2x80x9cIridium Projectxe2x80x9d, xe2x80x9cOdysseyxe2x80x9d, xe2x80x9cGlobal Starxe2x80x9d and xe2x80x9cInmarsat-Pxe2x80x9d in order to bring them into practice.
In the mobile communication system utilizing non-geostationary satellites, one communication terminal outputs radio waves of the same degree as those for a current portable telephone and performs communications with another communication terminal via a communication satellite.
In recent years, a GPS (Global Positioning System) which measures a current position through the use of a GPS satellite has been generally utilized. A navigation apparatus which is mounted in a vehicle is mainly adopted in the GPS. Of late, however, a portable GPS reception apparatus has also been employed in accordance with the miniaturization of a GPS reception unit which receives radio waves from a GPS satellite. In Europe and the United States, a DGPS (Differential Global Positioning System) in which a fixed reception station accurately receives radio waves from a GPS satellite and correction data is created based on the received radio waves, is also utilized in order to improve the measurement accuracy in the GPS.
The mobile radiotelephone systems such as a cellular telephone and the PHS are basically those for achieving a call between communication terminals through a relay radio base station. According to those systems, however, it is also possible to realize a long-distance call between communication terminals and to establish a connection between a communication terminal and a public line network. According to the mobile radiotelephone systems, a service area is divided into radio zones known as intermediate-distance area cells or short-distance area microcells. Radio base stations are provided in the individual radio zones and are in charge of them. The radio base stations are connected to each other via a private line network or a public line network, due to which a call can be made between communication terminals which differ in radio zone and which are far distant from each other, as well as between a communication terminal and a subscriber""s telephone connected to the public line network.
In principle, the mobile radiotelephone systems can realize a call when a communication terminal is present in a radio zone where the communication terminal can receive radio waves from a radio base station. In order to cover all areas as the radio zones, the mobile radiotelephone systems have to be provided with a large number of radio base stations.
Depending on country and system, the mobile radiotelephone systems differ from each other in radio frequency, connection method, communication protocol and standards for the communication terminals. These differences make mutual connection and data exchange impossible, which results in that a communication terminal, which is adopted in one mobile radiotelephone system, cannot be used in another mobile radiotelephone system.
In the mobile communication systems such as the xe2x80x9cIridium Projectxe2x80x9d, xe2x80x9cOdysseyxe2x80x9d, xe2x80x9cGlobal Starxe2x80x9d, xe2x80x9cInmarsat-Pxe2x80x9d, etc. which are being planned now, communications are performed using non-geostationary satellites. In general, a geostationary satellite travels along a stationary orbit whose height is 36,000 km. Meanwhile, a non-geostationary satellite travels along a low earth orbit or a medium earth orbit. The height of the low earth orbit is approx. 500 km to several thousand kilometers, and is lower than that of the orbit of the geostationary satellite. The height of the medium earth orbit is approx. 10,000 km, and is located inside the Van Allen belts. In the mobile communication systems utilizing non-geostationary satellites, since the height of the orbit of a communication satellite is low, the radio wave propagation delay time is short and the propagation loss of radio waves is small. Those permit the size and weight of a communication unit, etc., which are mounted in the communication terminal or the communication satellite, to be reduced.
The mobile communication systems utilizing non-geostationary satellites have an advantage in that a call area, which is considerably wider than a radio zone (call area) where radio waves can be received from a radio base station, can be attained. However, the above-mentioned mobile communication systems have the following problem:
A non-geostationary satellite moves relative to the earth at high speed, and accordingly the period of time over which the communication satellite stays in a communicable area, where it can communicate with a communication terminal, is short. In the case where the non-geostationary satellite moves in an orbit whose height is 1,000 km, the period of time over which the satellite stays in the communicable area, which begins at a specific point on the ground, is only twelve minutes. In order to enable a call to be made continuously from the specific point on the ground, a large number of non-geostationary satellites are required, and those satellites have to be successively located in communicable areas where they can communicate with the communication terminal. Since the speed at which the non-geostationary satellites move relative to the earth is high, a frequency shift due to the Doppler effect is considerable.
The antennas and the bodies of the communication terminal, which are employed in the mobile communication systems utilizing the non-geostationary satellites, can be made smaller in size than those employed in a system employing a geostationary satellite, but have larger sizes than those employed in the mobile radiotelephone systems. In the mobile communication systems utilizing the non-geostationary satellites, the communication fees are more expensive than those in the mobile radiotelephone systems, because the costs of launching and controlling a large number of communication satellites are huge.
In order to bring the communication fees down close to the fees charged for use of the mobile radiotelephone systems, it has been considered to employ, in the mobile communication systems utilizing the non-geostationary satellites, dual-mode communication terminals which contain communication circuits for the mobile radiotelephone systems so that not only the mobile communication systems but also the mobile radiotelephone systems can be utilized. According to the mobile communication systems utilizing the non-geostationary satellites and employing the dual-mode communication terminals, when the communication terminals can be connected to radio telephone base stations, the mobile radiotelephone systems, not the mobile communication systems, are utilized in order to reduce the total fees.
In the mobile radiotelephone systems such as the PHS in which a service area is divided into small radio zones, a communication terminal regularly receives an ID code from a radio base station, and identifies the radio base station which is in charge of a radio zone. When the communication terminal receives another different ID code, the communication terminal discriminates that it has moved to another radio zone, and sends a control signal to another radio base station which is in charge of the radio zone to which the communication terminal has moved. The radio base station receives the control signal sent from the communication terminal, and registers information about the communication terminal in the database of a network control apparatus which controls the radio base station. When calling up the communication terminal, the network control apparatus sends out a call signal to the communication terminal through the radio base station in accordance with the communication terminal information registered in the database, and establishes a line connection. In order to connect a line to the communication terminal, the network control apparatus needs to constantly check in which radio zone the communication terminal is located. Meanwhile, the communication terminal needs to regularly receive an ID code sent from the radio base station, which results in an increase in the power consumption.
In the case of a mobile communication system employing a geostationary satellite which moves in an orbit whose height is 36,000 km, the communicable area is wide, since the altitude of the communication satellite is high. In the mobile communication system utilizing a geostationary satellite, the communication satellite need not register or control the communication terminal, because the communicable area is fixed. On the other hand, in the mobile communication systems utilizing the non-geostationary satellites which move in the orbits whose heights are lower than that of a geostationary satellite, the communicable area changes from one to another in accordance with the movement of the communication satellite, and therefore the communication satellite needs to register and control the communication terminal.
In the mobile communication systems utilizing the non-geostationary satellites, unlike in the case of the mobile radiotelephone systems, the communication satellite is always moving relative to the earth, and the speed of its movement is considerably high. The network control apparatus has to frequently register the communication terminal and the communication satellite corresponding to the communication terminal in the database. Meanwhile, the communication terminal has to frequently receive an ID signal sent from the communication satellite. Consequently, according to the mobile communication systems utilizing the non-geostationary satellites, the important communication line and the electric power of the communication terminal are consumed due to such control procedures other than communications.
In order to eliminate the need to perform such control procedures other than communications in the mobile communication systems utilizing the non-geostationary satellites, it has been proposed to measure the position of the communication terminal, determine from the position of the communication satellite the communication satellite which becomes possible to communicate with the communication terminal, and perform communications via the communication satellite. Two methods for measuring the position of the communication terminal are available. According to one method, the communication satellite measures the position of the communication terminal. According to the other method, the communication terminal measures its position. However, those two methods have the following problems:
According to one method in which the communication satellite measures the position of the communication terminal, as well as in the case of an Emergency Position Indicating radio Beacon, the communication terminal has to constantly or frequently send position measurement data to the communication satellite, under which condition the communication terminal consumes a large amount of power. In the case where the number of system subscribers increases, the communication satellite is required to process position measurement data sent from a huge number of communication terminals, which entails the need to provide the satellite with a large-scale processing unit.
According to the other method in which the communication terminal measures its position, three or four communication satellites are located in the sky and send position measurement data in the same principle as that of the GPS. In this method, the number of communication satellites, the determination and arrangement of the orbit are limited. The communication satellites send the position measurement data to the communication terminal, and relay, to an earth station, position information sent from the communication terminal. The communication terminal thus requires a circuit for receiving the position measurement data, and consumes a large amount of power in order to receive the position measurement data.
The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide communication apparatus, communication control apparatus, a portable communication apparatus and a communication control method, all for enabling efficient communications to be attained with low power consumption.
Another object of the present invention is to provide a communication apparatus, a communication control apparatus, a portable communication apparatus and a communication control method, all for determining communication conditions such as the arrival time and location at which communications with a communication satellite and a radio base station become possible, etc. and for enabling efficient communications to be attained.
According to the first aspect of the present invention having the above-described object, there is provided a communication terminal apparatus comprising:
orbit calculation means (29, 73, 125, 217, 324) for calculating position of a communication satellite which is changing;
current position discrimination means (15, 82, 125, 217, 305) for discriminating a current position of said communication terminal apparatus on the earth;
determination means (29, 73, 128, 220, 324) for determining whether said communication satellite has arrived a communicable area in which said communication satellite is capable of communicating with said communication terminal apparatus, based on the position of said communication satellite which said orbit calculation means (29, 73, 125, 217, 324) has calculated and the current position of said communication terminal apparatus which said current position discrimination means (15, 82, 125, 217, 305) has discriminated;
satellite communication means (3, 54, 103, 204, 306) for communicating with said communication satellite; and
communication control means (4, 94, 122, 223, 328) for controlling said satellite communication means (3, 54, 103, 204, 306) to start and stop communications, in accordance with the result of the determination performed by said determination means (29, 73, 128, 220, 324).
Said orbit calculation means may include:
storage means for storing orbital element data specifying the shape of an orbit of said communication satellite and the motion of said communication satellite, and
means (29, 73, 125, 217, 324) for calculating a geocentric position of said communication satellite which is the position relative to the earth, by performing orbital calculations based on the orbital element data stored in said storage means.
Said determination means (29, 73, 128, 220, 324) includes, for example, position determination means (38, 73, 128, 229, 324) for determining whether said communication satellite has arrived said communicable area and whether said communication satellite has left said communicable area.
Said current position discrimination means (15, 82, 125, 217, 305) may includes position input means (23) for inputting information representing the current position of said communication terminal apparatus on the earth.
Said current position discrimination means (15, 82, 125, 217, 305) may include position measurement calculation means (82, 135, 217, 305) for measuring and calculating the current position of said communication terminal apparatus on the earth.
Said position measurement calculation means (82, 135, 217, 305) may include means (15, 82, 125, 217, 305) for receiving signal radio waves from a GPS satellite and deriving the current position of said communication terminal apparatus on the earth by performing predetermined position measurement and calculation based on the received signal radio waves.
Said position measurement calculation means (82, 135, 217, 305) and said satellite communication means (3, 54, 103, 204, 306) may share at least a part of an antenna and at least a part of a communication circuit.
Said determination means (29, 73, 128, 220, 324) may include calculating determination means (29, 73, 128, 220, 324) for calculating at least one of an arrival time at which said communication satellite is to arrive said communicable area and a leaving time at which said communication satellite is to leave said communicable area, and for determining, based on the result of the calculation, whether said communication satellite has arrived said communicable area. In this case, said communication control means (4, 94, 122, 223, 328) controls said satellite communication means to start and stop communications, in accordance with the result of the determination performed by said calculating determination means.
Said determination means and said communication control means (4, 94, 122, 223, 328) may include:
calculating means (128) for calculating at least one of an arrival time at which said communication satellite is to arrive said communicable area and a leaving time at which said communication satellite is to leave said communicable area;
storing means (131) for storing the at least one of the arrival time and leaving time;
timer (129) for counting current time; and
comparing means (130, 131) for comparing the current time and the time stored in said storing means, and controlling said satellite communication means to start and stop communications, in accordance with the result of the comparison by said comparing means.
Said communication control means (4, 94, 122, 223, 328) may include power supply control means (31, 76, 139, 329) for controlling turning on and off of a power supply to said satellite communication means (3, 54, 193, 294, 306).
Said satellite communication means (3, 54, 193, 294, 306) may include communication means (227) which employs at least one of a spread spectrum modulation and demodulation system and a code division multiple access system.
Said orbit calculation means (29, 73, 125, 217, 324) may include storage means (22) for storing orbital element data created by demodulating and decoding a signal which said satellite communication means (3, 54, 103, 204, 306) has received from said communication satellite, and means (29, 73, 125, 217, 324) for calculating the position of said communication satellite by using the orbital element data stored in said storage means (22).
The communication apparatus may comprises
display means (453, 118, 215) for displaying data,
position calculation means (29, 73, 128, 217, 324) for calculating communication satellite position information, based on at least one of orbit position information specifying a position of the orbit of said communication satellite, geocentric position information specifying a geocentric position of said communication satellite and apparent position information specifying an apparent position of said communication satellite, and
display control means (14, 66, 116, 214, 320) for controlling said display means (453, 118, 215) to display, at least in one of the form of character data and the form of plot image data, the communication satellite position information calculated by said position calculation means (29, 72, 128, 217, 324).
The communication apparatus may be a fitted-on type communication terminal apparatus which is fitted on a part of a body of a user.
Said communication apparatus may include an antenna element (2, 52, 102, 202, 303) which is used to perform communications via said communication satellite. Said antenna element includes, for example, a helical type antenna, a dielectric antenna or a patch type flat antenna.
To achieve the objects, a communication apparatus according to the second aspect of the present invention comprises:
orbit calculation means (29, 73, 125, 217, 324) for calculating a position of a communication satellite;
current position discrimination means (15, 82, 125, 217, 305) for discriminating a current position of said communication terminal apparatus on the earth;
determination means (29, 73, 128, 220, 324) for determining whether said communication satellite has arrived a communicable area in which said communication satellite is capable of communicating with said communication terminal apparatus, based on the position of said communication satellite which said orbit calculation means (29, 73, 125, 217, 324) has calculated and the current position of said communication terminal apparatus which said current position discrimination means (15, 82, 125, 217, 305) has discriminated;
satellite communication means (3, 54, 103, 204, 306) for communicating with said communication satellite;
ground communication means (142, 204, 307) for performing communications via a earth radio base station; and
communication control means (131, 221, 328) for controlling said ground communication means (142, 204, 307) to stop communications and controlling said satellite communication means (3, 54, 103, 204, 306) to start communications, when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is in said communicable area, and for controlling said satellite communication means (3, 54, 103, 204, 306) to stop communications and controlling said ground communication means (142, 204, 307) to start communications, when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is not in said communicable area.
Said ground communication means (142, 204, 307) may include identification code detection means (146, 231, 307) for receiving and detecting an identification code sent from said earth radio base station, and said communication control means (131, 221, 328) may include means (116, 214, 320) for controlling said ground communication means (142, 204, 307) to start communications, when said identification code detection means (146, 231, 307) detects the identification code sent from said earth radio base station, and for controlling said satellite communication means (3, 54, 103, 204, 306) to start communications, when said identification code detection means (146, 231, 307) does not detect the identification code sent from said earth radio base station and when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is in said communicable area
Said ground communication means (142, 204, 307) may includes waiting reception means (116, 214, 320), which waits a call from said earth radio base station, for performing communications upon receiving the call from said earth radio base station.
Said ground communication means (142, 204, 307) and said satellite communication means (3, 54, 103, 204, 306) may share at least a part of an antenna and at least a part of a communication circuit.
To achieve the objects, a communication apparatus according to the third aspect of the present invention comprises:
ground communication means (142, 204, 307) for performing communications via a earth radio base station;
current position detection means (125, 217, 305) for detecting a current position of said communication terminal apparatus on the earth and outputting current position information specifying the detected current position;
communication condition information storage means (326) for storing communication condition information including communication area position information specifying a position of a communication area where said ground communication means (142, 204, 307) is capable of performing communications;
area discrimination means (325) for discriminating whether said communication terminal apparatus is in said communication area, based on the current position information output from said current position detection means (125, 204, 307) and the communication area position information stored in said communication condition information storage means (326); and
communication control means (131, 221, 328) for controlling said ground communication means (142, 204, 307) to start communications, when said area discrimination means (325) discriminates that said communication terminal apparatus is in said communication area, and for controlling said ground communication means (142, 204, 307) to stop communications, when said area discrimination means (325) discriminates that said communication terminal apparatus is not in said communication area.
Further, a communication apparatus according to the fourth aspect of the present invention, comprises:
orbit calculation means (29, 73, 125, 217, 324) for calculating a position of a communication satellite;
current position detection means (125, 217, 305) for detecting a current position of said communication terminal apparatus on the ground and outputting current position information specifying the detected current position;
determination means (29, 73, 128, 229, 324) for determining whether said communication satellite has arrived a communicable area where said communication satellite is capable of communicating with said communication terminal apparatus, based on the position of said communication satellite which said orbit calculation means (29, 73, 125, 217, 324) has calculated and the current position of said communication terminal apparatus which said current position detection means (125, 217, 305) has detected;
satellite communication means (3, 54, 103, 204, 306) for communicating with said communication satellite;
ground communication means (142, 204, 307) for performing communications via a ground radio base station;
communication condition information storage means (326) for storing communication condition information including communication area position information specifying a position of a communication area where said ground communication means (142, 204, 307) is capable of performing communications;
area discrimination means (325) for discriminating whether said communication terminal apparatus is in said communication area, based on the current position information output from said current position detection means (125, 204, 307) and the communication area position information stored in said communication condition information storage means (326); and
communication control means (131, 221, 328) for controlling said ground communication means (142, 204, 307) to start communications, when said area discrimination means (325) discriminates that said communication terminal apparatus is in said communication area, and for controlling said satellite communication means (3, 54, 103, 204, 306) to start communications, when said area discrimination means (325) discriminates that said communication terminal apparatus is not in said communication area.
A communication control apparatus according to the fifth aspect of the present invention comprises:
communication satellite position detection means (29, 73, 128, 217, 324) for detecting a position of a communication satellite which is changing;
terminal position detection means (82, 125, 217, 305) for detecting a current position of said communication terminal on the earth;
determination means (29, 73, 128, 220, 324) for determining whether said communication satellite has arrived a communicable area where said communication satellite is capable of communicating with said communication terminal, based on the position of said communication satellite which said communication satellite position detection means (29, 73, 128, 217, 324) has detected and the current position of said communication terminal which said terminal position detection means (82, 125, 217, 305) has detected;
satellite communication means (3, 54, 103, 204, 306) for communicating with said communication satellite;
ground communication means (142, 204, 307) for performing communications via a ground radio base station;
communication control means (131, 221, 328) for controlling said ground communication means (142, 204, 307) to stop communications and controlling said satellite communication means (3, 54,103, 204, 306) to start communications, when said determination means (29, 73,128, 220, 324) determines that said communication satellite is in said communicable area, and for controlling said satellite communication means (3, 54, 103, 204, 306) to stop communications and controlling said ground communication means (142, 204, 307) to start communications, when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is not in said communicable area.
A communication control apparatus according to sixth aspect of the present invention includes:
calculation means (29, 73,128, 217, 324) for detecting a position of a communication satellite which is changing;
a position measurement calculation means (82, 125, 217, 305) for detecting a current position of said communication terminal on the earth;
a control circuit (14, 66, 116, 214, 320) for determining whether said communication satellite has arrived a communicable area where said communication satellite is capable of communicating with said communication terminal, based on the position of said communication satellite which said azimuth calculation means (29, 73,128, 217, 324) has detected and the current position of said communication terminal which said position measurement calculation means (82, 125, 217, 305) has detected;
a satellite communication circuit (3, 34, 103, 204, 306) for communicating with said communication satellite;
a radio communication circuit (142, 204, 307) for performing communications via a ground radio base station; and
a communication control circuit (131, 221, 328) for controlling said radio communication circuit (142, 204, 307) to stop communications and controlling said satellite communication circuit (3, 54, 103, 204, 306) to start communications, when said control circuit (14, 66, 116, 214, 320) determines that said communication satellite is in said communicable area, and for controlling said satellite communication circuit (3, 54, 103, 204, 306) to stop communications and controlling said radio communication circuit (142, 204, 307) to start communications, when said control circuit (14, 66, 116, 214, 320) determines that said communication satellite is not in said communicable area.
To achieve the object, a fitted-on type communication terminal apparatus according to the seventh aspect of the present invention has a main body which is fitted on a part of a body of a user, said main body including:
communication satellite position detection means (29, 73, 128, 217, 324) for detecting a position of a communication satellite;
terminal position detection means (82, 125, 217, 305) for detecting a current position of said main body;
determination means (29, 73, 128, 220, 324) for determining whether said communication satellite is in a communicable area where said communication satellite is capable of communicating with said main body, based on the position of said communication satellite which said communication satellite position detection means (29, 73, 128, 217, 324) ha detected and the current position of said main body which said terminal position detection means (82, 125, 217, 305) has detected;
satellite communication means (3, 54, 103, 204, 306) for communicating with said communication satellite;
ground communication means (142, 204, 307) for performing communications via a ground radio base station; and
communication control means (131, 221, 328) for controlling said ground communication means (142, 204, 307) to stop communications and controlling said satellite communication means (3, 54, 103, 204, 306) to start communications, when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is in said communicable area, and for controlling said satellite communication means (3, 54, 103, 204, 306) to stop communications and controlling said ground communication means (142, 204, 307) to start communications, when said determination means (29, 73, 128, 220, 324) determines that said communication satellite is not in said communicable area.
A communication control method according to the eighth aspect of the present invention comprises the steps of:
a communication satellite position detecting step (S2) of detecting a position of a communication satellite which is a position relative to the earth and which is changing;
a terminal position detecting step (S4) of detecting a current position of a communication terminal apparatus;
a determining step (S4) of determining whether said communication satellite has arrived a communicable area where said communication satellite is capable of communicating with said communication terminal apparatus, based on the position of said communication satellite which has been detected by said communication satellite position detecting step (S2) and the current position of said communication terminal apparatus which has been detected by said terminal position detecting step (S4); and
a communication controlling step of stopping communications performed via a ground radio station and starting communications with said communication satellite when it is detected in said determination step (S4) that said communication satellite is in said communicable area, and stopping communications with said communication satellite and starting communications via said ground radio base station when it is detected in said determination step (S4) that said communication satellite is not in said communicable area.